This invention relates generally to a fuel pump and more particularly to a regenerative or turbine type fuel pump.
Electric motor fuel pumps have been widely used to supply the fuel demand for an operating engine such as in automotive applications. These pumps may be mounted directly within a fuel supply tank with an inlet for drawing liquid fuel from the surrounding tank and an outlet for delivering fuel under pressure to the engine. The electric motor includes a rotor mounted for rotation within a stator in a housing and connected to a source of electrical power for driving the rotor about its axis of rotation. In the pump, an impeller is coupled to the rotor for co-rotation with the rotor and has a circumferential array of vanes about the periphery of the impeller. One example of a turbine fuel pump of this type is illustrated in U.S. Pat. No. 5,257,916.
Conventional fuel pump impellers have vanes which are generally flat, straight and radially outwardly extending. Other impeller vanes have been flat, straight and canted relative to a radius of the impeller. With this general configuration, previous fuel pumps have had an efficiency of approximately 20% to 30% and when combined with an electric motor having a 45% to 50% efficiency, the overall efficiency of such electric motor turbine-type fuel pumps is between about 10% to 15%. Thus, there is the continuing need to improve the design and construction of such fuel pumps to increase their efficiency.
U.S. Pat. No. 5,642,981 (the ""981 patent) discloses an open channel fuel pump with an impeller and various vane shapes and configurations for the impeller. In FIG. 13E, a vane is shown which has a base portion extending radially from a body of the impeller over a length of approximately 80% of the total length of the vane, and a tip portion extending from the base portion which is curved or arcuate so that the tip portion leads the base portion in the direction of rotation of the impeller. The open channel pump design communicates pockets between adjacent vanes, that are formed on each of the opposed faces of the impeller, with each other.
An electric motor turbine-type fuel pump having a pair of substantially separate fuel pumping channels on opposed faces of an impeller which has a plurality of circumferentially spaced vanes disposed about the periphery of the impeller. Each vane has a base portion extending essentially radially outwardly from a main body of the impeller and a tip portion extending from the base portion. The tip portion of each vane is generally arcuate or curved such that a radially outermost edge of the tip is forward of or leads the corresponding radially innermost edge of its base relative to the direction of rotation of the impeller. Preferably, each vane is defined between a pair of radially, axially, and circumferentially extending pockets formed in the impeller, with one set of vanes opening to each of a pair of opposed side faces of the impeller. An axially centered, circumferentially extending rib extends to the radially outermost portion of the vanes and separates the vanes on one face of the impeller from the vanes on the opposed face of the impeller. The center rib communicates with a complementary rib of a guide ring in which the impeller is received in assembly of the fuel pump to also separate the pair of fuel pumping channels from each other. The orientation of the vanes within the split or separated fuel pumping channels dramatically increases the efficiency of the fuel pump, especially during conditions of low fuel pump motor speeds and low fuel flow rate conditions in the fuel pump. Desirably, this will, for example, improve the cold starting of an engine utilizing the fuel pump.
Objects, features and advantages of this invention include providing an improved impeller for a turbine-type fuel pump which improves the efficiency of the fuel pump, improves the circulation of fuel through a pair of pumping channels defined about the periphery and adjacent opposed faces of the impeller, can be used with existing fuel pump designs, has dramatically improved performance at low fuel pump motor speeds and low fuel flow rates, improves cold starting of an engine to which it supplies fuel, is rugged, durable, of relatively simple design and economical manufacture and assembly and has a long useful life in service.